A comprehensive assessment of the impact of errors in the cancer registration process on 1- and 5-year relative survival estimates.

BACKGROUND: When making international comparisons of cancer survival, it is essential reported differences are real effects and not an artefact of potential errors in cancer registration. METHODS: We use simulation methods to assess the impact of various cancer registration errors on commonly reported outcomes of cancer survival (1-, and 5-year relative survival estimates). We draw two samples of patients diagnosed with cancer from one population and introduce potential registration errors in one of the sample populations under various assumptions. We investigate the effect of errors individually as well as the composite effect when combined with other registration errors. RESULTS: The results indicate that high levels of cancer registration errors are necessary to make a noticeable effect on commonly reported metrics of cancer survival. Differences of up to 3 percentage units in the 5-year relative survival proportion are seen under plausible scenarios. CONCLUSION: This study is a comprehensive assessment of cancer registration errors and the consequent impact on commonly reported survival statistics. We show that under plausible scenarios, it is very unlikely that these biases are large enough to explain the variation in international comparisons of cancer survival. Registration errors will also impact on other metrics reported from registry data, such as incidence.